Lossless data compression schemes such as zip for compressing data structures are well known. However, the zip format in its current standard implementation has developed such that it supports only file or directory names containing characters from a restricted set of characters, namely ISO-Latin-1 (ISO 8859-1) characters. Such a restricted character set includes, for example, letters of the Roman alphabet (upper and lower case) additional common accented characters (á, ö etc.) numerical values, punctuation symbols and so forth and is effectively an extension of the ASCII character set. As a result problems can be encountered when attempting to zip data structures including file or directory names comprising characters not from the restricted character set. According to one existing solution, a version of zip has been created allowing the use of Japanese characters in file or directory names, but this extension is limited only to the alternative character set and in fact is not compatible even with the ISO-Latin-1 version.